So you think leftists can't infiltrate and take over organizations like the right can?
Not the cops, no. Of course not. By the time the left was large enough to try that it would have no need to, but really it is inherently a far-right institution. It's like saying your big plan is to infiltrate and take over the Nazis by doing Nazi things for decades. Friend, you don't do that, it is counterproductive. You shoot the Nazis.
As I said in my other comment, the right isn't "infiltrating" the cops. The cops have always been far right.
Taking down from within is a fully valid tactic when dealing with an enemy dude.
Being this vague means it is an unserious idea. It feels like we are talking about cartoons or Batman vs. Superman or something. The only orgs the left can usefully take over - really, lead - are those with which we have some kind of alignment and expectation of useful outcomes. Historically, institutions like unions. Even then, we are not taking them over, we are gaining trust and power so that we can ensure alignment of organized labor with our ends rather than those of the ruling class, which will constantly try to defang labor.
Cops are our enemies. They are, inherently, a force for ruling class interests. The only valid end goal of "infiltration" would be to get them to all shoot each other or something, and even that is silly because they're not going to do that because we are sheriffs or something. They would do that if their little gangs have turf wars due to a destabilized state.